The present invention relates generally to a structural reinforcement system for use in increasing the stiffness, strength, durability, sealing, and sound absorption/damping of different portions of a variety of goods and products, such as furniture, commercial, industrial, and household appliances, as well as land transportation vehicles, such as automotive, aerospace, marine, and rail vehicles. More particularly, the present invention relates to segmented or modularly expandable structurally reinforced closed forms, such as a hydroform structure or hydroform rail, which utilizes a plurality of segmented parts suitable for flexible attachment and capable of providing a unitary structure for reinforcement of a desired area. Once attached as a whole, the segmented portions maintain flexibility for movement and application into specific closed form shapes while the exterior surface of each individual segment or module can be coated with a material selected from a group consisting of a sealing material, or sound damping material, an anti-vibration material, a structurally reinforcing material, or other expandable and foamable material to cross-link, structurally adhere, and reinforce the form when the material becomes chemically active and expands upon heating, self-heating, or is otherwise exposed to a heat or energy source.
Traditionally, closed form or hydroforming techniques are used to draw and shape metal tubes. Conventional hydroforming techniques often involve two steps: (1) placing the desired bends in the tube and (2) forming the tube to the desired configuration. The second step of this process usually requires placing a tubular member having an open bore in a mold and pinching off the ends of the tube. A pressurized liquid is then injected into the open bore, causing the tube to stretch and expand out against the mold.
The manufacturing advantages of the hydroforming process is that it allows formation of relatively long tubular structures having a seamless perimeter. This process eliminates the cost of welding, machining, or fastening operations often used to shape the part in the desired configuration. As a result, a hydroform or closed form structure very often has a high length to diameter ratio. For instance, a hydroform structure may have a length in excess of 15xe2x80x2 and a diameter ranging from approximately xc2xexe2x80x3 to more than 12xe2x80x3. To this end, a further manufacturing process advantage of a hydroform structure is that it can exceed the length of other tubular members, such as torsion bars or tubular bars, formed using other processes.
Additionally, hydroforming processing creates complex structural shapes that typically include bends and contour changes. Often the number of bends and contour changes in a hydroformed bar are greater and more complex than those found in torsion bars or other tubular structures formed using different techniques. These shapes often have particular application in land transportation vehicles which require contour changes to reflect vehicle styling and traditional automotive architecture in the form of automotive rails, pillars, and other structural members.
In addition, hydroform structures typically have a constant wall thickness prior to forming, and might develop strength differences at the site of bends or changes in contour, as well as at certain locations along a long tubular section. Thus, it is often desirable to reinforce closed form and hydroform sections to improve their structural stiffness, strength, and durability, particularly in automotive vehicle applications.
Traditional ways of reinforcing tubular structures such as hydroforms and other closed forms include sliding a metal sleeve inside the tube and welding the reinforcing member in place. However, because the hydroform often includes one or more shapes or bends, or one or more changes in contour and/or diameter, it is often difficult to insert the sleeve into the hydroform at the precise location of the weak portion. Other techniques include reinforcing the hydroform from the outside by welding the sleeve onto the outside of the hydroform. However, hydroforms are often used in applications having very close tolerances, resulting in little or no clearance for an externally placed reinforcing member. Accordingly, exterior reinforcements are often not as effective as interior reinforcements.
Additionally, in many operations the weight of the tubular member is critical and must be kept low as possible. Thus, the use of an external sleeve adds unwanted weight to the tubular assembly. Still further, the welding operation tends to be labor intensive during the manufacturing process, time consuming and inexact, increasing the cost of forming the hydroform member and producing parts that have questionable reliability. Finally, these additional manufacturing steps and operations are often cumbersome and difficult to integrate into a final vehicle manufacturing process in that additional tooling would need to be developed by the manufacturer and assembly plant resources, labor, maintenance, and space would need to be dedicated and expensed by the vehicle manufacturer.
Accordingly, there is a need in industry and manufacturing operations for system, device, and method for reinforcing the weak areas of closed forms and other hydroform tubes, such as a hydroform rail, without significantly increasing the weight and manufacturing complexity. In particular, there is a need for reinforcing a closed form or hydroform, which utilizes a plurality of segments or portions to achieve integrated reinforcement within the closed form since the contour or shape of typical tubes do not allow for placement of single piece reinforcement members. In this regard, the present invention addresses and overcomes the shortcomings found in the prior art by providing a multi-segment reinforcement system having at least two segments or portions capable of being modularly attached or otherwise engaged in segments within a hydroform that may then be fixed in location through the use of a third segment or portion which serves as a locking, positioning, and retaining member of the reinforcement system within the hydroform or other closed form. However, the plurality of modularly attached segments could also be locked, positioned, and retained within a hydroform through the use of retention means, such as a string, wire, or chain looped through each of the segments which provides enough tension to retain each of the segments in a desired position while the entire system (i.e. the segments with an amount of bonding material disposed along at least a portion of each of the segments) is exposed and cured by the heat typically encountered in an automotive painting operation. Structural reinforcement of the hydroform is achieved through activation by heat of the bonding material disposed along at least a portion of an outer or exterior surface of the plurality of segments or portions, such a material would typically expand when exposed to heat or other energy source and in doing so structurally adhere the segments or portions to each other and the hydroform. Further, it is contemplated that the system would have greater flexibility to a range of applications by allowing each segment or portion of the plurality of segments to also have the capability of receiving a suitable amount of sealing material, sound absorption material, and/or an expandable material, or a combination thereof.
The present invention relates to methods and systems for reinforcing a closed form or hydroform member. In one embodiment, the system includes a plurality of segments having a bonding material disposed over at least a portion of the exterior or outer surface of the segments which may or may not be expandable upon exposure to heat or other energy source. The selected bonding material extends along at least a portion of the exterior surface of at least one segment which are then configured for placement within a portion of a automotive vehicle to be reinforced.
In a particular preferred embodiment, the bonding material consists of an expandable material which is generally and preferably a heat-activated epoxy-based resin having foamable characteristics upon activation through the use of heat typically encountered in an e-coat process, paint oven, or other automotive painting operation. As the material is heated or otherwise exposed to an energy source in the manufacturing environment, it expands, cross-links, and structurally adheres to adjacent surfaces. Preferred structural foam or expandable materials are commercially available from LandL Products, Inc. of Romeo, Mich. under the designation L5204, L5206, L5207, L5208, or L5209. Generally speaking, these automotive vehicle applications may utilize technology and processes such as those disclosed in U.S. Pat. Nos. 4,922,596, 4,978,562, 5,124,186, and 5,884,960 and commonly owned, co-pending U.S. application Ser. Nos. 09/502,686 filed Feb. 11, 2000, 09/524,961 filed Mar. 14, 2000, and particularly, 09/459,756 filed Dec. 10, 1999, all of which are expressly incorporated by reference.
The system generally employs two or more segments or portions defined adapted for stiffening the structure to be reinforced and helping to redirect applied loads. In use, the segments are inserted into a closed form, such as a hydroformed tube, or simply placed or retained in a cavity by retention means defined within portions of an automotive vehicle such as a pillar, rail, rocker, door assembly, or other frame member, with the heat activated bonding material serving as the load transferring and potentially energy absorbing medium. In a particularly preferred embodiment, at least two of the segments are composed of a polymeric material, such as nylon, an injection molded nylon carrier, an injection molded polymer, graphite, carbon, or a molded metal (such as aluminum, magnesium, and titanium, an alloy derived from the metals or a metallic foam derived from these metals or other metal foam) and is at least partially coated with a bonding material on at least one of its sides, and in some instances on four or more sides. A preferred bonding material is an epoxy-based resin, such as L5204, L5206, L5207, L5208 or L5209 structural foam commercially available from L and L Products, Inc. of Romeo, Mich. However, the present invention may further comprise retention means in an alternative form consisting of a third member, segment, or portion which serves to lock and position the at least first two segments in place. This retention means could also utilize an adhesive material disposed along an outer surface of each of the members, segments, or portions. Still further, the retention means, which serves to lock, position, and retain the plurality of members or segments within the hydroform could also comprise locking means, such as a string, wire, or chain looped through each of the segments which provides enough tension to retain the plurality of segments in a desired position while the bonding material is activated in the e-coat or painting operation. Once the bonding material is activated and cured, it is contemplated that the bonding material will structurally secure and retain the plurality of segments in the desired position within the portion of the vehicle to be reinforced.
In addition, it is contemplated that the plurality of segments could comprise a nylon or other polymeric material as set forth in commonly owned U.S. Pat. No. 6,103,341, expressly incorporated by reference herein. Still further, the segments adapted for stiffening the structure to be reinforced could comprise a stamped and formed cold-rolled steel, a stamped and formed high strength low alloy steel, a stamped and formed transformation induced plasticity (TRIP) steel, a roll formed cold rolled steel, a roll formed high strength low alloy steel, or a roll formed transformation induced plasticity (TRIP) steel, as well as an elastomer, polyethylene, ethylene-vinyl acetate copolymer, plasticized polyvinyl chloride film, polyamide, polysulfone, or various olfenic copolymer and terpolymer materials. Although the bonding material of the present invention does not need to be either heat-activatable or expandable, a preferred material used in the present invention is an expandable structural material. The choice of the material selected as the bonding material will be dictated by performance requirements and economics of a specific application.
Additional bonding materials that could be utilized in the present invention include other materials which are suitable as acoustic media (i.e. sound absorbing, sound damping, or impacting NVH characteristics) and which may be heat activated which generally activate and expand to fill a desired cavity or occupy a desired space or function when exposed to temperatures typically encountered in automotive e-coat curing ovens and other paint operations ovens. Though other heat-activated materials are possible, a preferred heat activated material is an expandable or flowable polymeric formulation, and preferably one that can activate to foam, flow, adhere, or otherwise change states when exposed to the heating operation of a typical automotive assembly painting operation. For example, without limitation, in one embodiment, the polymeric foam is based on ethylene copolymer or terpolymer that may possess an alpha-olefin. As a copolymer or terpolymer, the polymer is composed of two or three different monomers, i.e., small molecules with high chemical reactivity that are capable of linking up with similar molecules. Examples of particularly preferred polymers include ethylene vinyl acetate, EPDM, or a mixture thereof. Without limitation, other examples of preferred foam formulation that are commercially available include polymer-based material commercially available from LandL Products, Inc. of Romeo, Mich., under the designations as L-2105, L-2100, L-7005 or L-2018, L-7101, L-7102, L-2411, L-2420, L-4141, etc. and may comprise either open or closed cell polymeric base material.
Further, it is contemplated that the plurality of segments or portions of the present invention could employ a suitable amount of sealing, sound dampening, structural reinforcement, or acoustic material in combination upon different surfaces of the plurality of segments within the selected area to be reinforced to achieve specific points of reinforcement, sealing, and/or sound damping depending upon the individual needs or desirability of the specific application. When activated through the application of heat, it is contemplated that a segment specific material will achieve not only structural reinforcement, but may also assist in the reduction of vibration and noise in the overall automotive body depending upon the characteristics of the chosen bonding material. In this regard, the now reinforced area, closed form, or hydroform will have increased stiffness in the cross-members, which will shift the natural frequency, measured in hertz that resonates through the automotive chassis and will reduce acoustic transmission and the ability to block or absorb noise through the use of the conjunctive acoustic, sealing, or sound damping product. By increasing the stiffness and rigidity of the cross-members, the noise and frequency of the overall engine ride vibration that occurs from the operation of the vehicle can be reduced since a shift in frequency of noise and vibration will allow resonance through the chassis. Although the use of such sealing, damping, and vibration reducing materials or media can be utilized instead of, or in conjunction with, the structural expandable material on the individual segments of the present invention, the preferred embodiment of the structural reinforcement system of the present invention utilizes a bonding material consisting of a structurally reinforcing expandable material. Use of acoustic materials in conjunction with structural may provide additional structural improvement but primarily would be incorporated to improve NVH characteristics.
It is also contemplated that the material of the present invention could be delivered and placed into contact with the segments through a variety of delivery systems which include, but are not limited to, a mechanical snap fit assembly, extrusion techniques commonly known in the art as well as a mini-applicator technique as in accordance with the teachings of commonly owned U.S. Pat. No. 5,358,397 (xe2x80x9cApparatus For Extruding Flowable Materialsxe2x80x9d), hereby expressly incorporated by reference. In this non-limiting embodiment, the material is at least partially coated with heat-activated material that could be structural, sealing, dampening, or acoustic in nature. This preferably heat activated material can be snap-fit onto the chosen surface or substrate; placed into beads or pellets for placement along the chosen substrate or member by means of extrusion, placed along the substrate through the use of baffle technology, die-cut according to teachings that are well known in the art, utilize pumpable application systems which could include the use of a baffle and bladder system, as well as sprayable applications.
In another embodiment, the plurality of segments are composed of an injection molded nylon and provided with a suitable amount of bonding material or load transfer medium molded onto its sides in at least one location defining a portion wherein each portion is smaller in diameter than a corresponding insertable opening in the form or tube to enable placement within a cavity defined within an automotive vehicle, such as portions of a hydroform tube, hydroform rail, or other area or substrate found in an automotive vehicle which could benefit from the structural reinforcement characteristics found in the present invention. In this embodiment a plurality of modularly attachable segments or portions are utilized to provide an integrated member, having flexible characteristics relative to one another similar to the movements of an accordian, for installation within a hydrofromed rail or other area of a vehicle that would benefit from structural reinforcement. For example, a first segment or portion corresponds to, and is insertably attached to an opening located within the hydroform tube or hydrofrom rail section. A second segment or portion is modularly attachable or slideably engaged and affixed to a surface of the first segment or portion. A third segment or portion, and a plurality of portions thereafter, is then modularly attached or slideably engaged and affixed to a surface of the preceding plurality of segments. It is contemplated that the modularly attached or slideably engaged plurality of segments will still provide a certain degree of freedom or flexibility whereby the plurality of segments can flex and be shaped to fit within the contours or geometric requirements of the area to be structurally reinforced. A fixed locking member or retention means, such as a heal and toe feature, is then utilized to place or fix the plurality of segments or portions together within the area to be reinforced thereby retaining the segments. Further, the locking member could comprise tension means, such as a string, wire, chain, or cable retaining the plurality of segments with the bonding material on the exterior surface of the segments in a desired position while the system undergoes baking in an automotive painting operation. The bonding material is activated to accomplish expansion through the application of heat typically encountered in an automotive e-coat oven or other painting operation oven in the space defined between the plurality of segments or portions and the walls of the cavity selected for reinforcement. The resulting structure includes the wall structure of the hydroform tube or cavity joined to the plurality of segments with the aid of the now activated bonding material. It is contemplated that each individual segment or portion could be configured for application of a bonding material, expandable material, or sealing material applied in a variety of patterns, shapes, and thicknesses to accommodate the particular size, shape, and dimensions of the cavity corresponding to the chosen form or vehicle application.